The history of modern linguistics is dominated by its founding figure, Ferdinand de Saussure. The Cours de Linguistique Générale, published under his name, is regarded as the programmatic text of structuralism and is one of the most cited works in linguistics and cultural studies in recent decades. Ludwig Jäger's introduction reveals a largely unknown author of the same name behind this very present de Saussure, whose theoretical interests in the fields of language and sign theory developed from the laboratory experiences of a brilliant comparative linguist at the end of the 19th century. This Saussure, reconstructible from the sources, enters into a dialogue with his structuralist alter ego and is situated within the horizon of contemporary discourses.